This relates generally to devices that source and sink video and audio data.
DisplayPort is a digital audio/video interconnect standard of the Video Electronic Standards Association (VESA). It allows video and audio to be coupled from a computer to a video display or an audio playback system. The DisplayPort connector supports 1, 2, or 4 data pairs in a main link that also carries clock and optional audio signals with symbol rates of 1.62, 2.7, or 5.4 gigabits per second. A 1.1 standard was approved in May 2006 and in 2009 a 1.2 standard, with increased data rates, was announced. The DisplayPort 1.2 standard doubles the bandwidth of the 1.1 standard.
With the DisplayPort 1.2 standard, two WQXGA monitors may sink audio/video data from a single source link or four WUXGA monitors may sink data from a single source link. In addition, the 1.2 standard allows a higher speed AUX which may be used for Universal Serial Bus (USB) peripheral device data transfer, microphone audio transfer, or camera video transfer, to mention a few applications.
Display or sink devices can be connected to source devices, such as personal computers or consumer electronic devices, either directly or through what are called branch devices. Many types of branch devices exist including repeaters that repeat audio or video information, converters that convert audio or video information from one format to another, replicaters, which reproduce the data, and concentrators that take streams from two or more source devices as inputs and transmit them on its downstream links. Interface standards, such as DisplayPort 1.2, allow multiple streams on one link; in such cases, these two or more input streams may be transmitted onto a single downstream link. Some concentrators may operate in a switched fashion, i.e. only one selected source may transmit at a time.
Together, the source, sink, and branch devices form a topology in which a given source may be streaming video to one or more sinks through zero or more branch devices. Active video data flows through links connecting various device types. Each link is constrained by its bandwidth and the number of streams that it supports. A sink will have a limited number of audio and video endpoints to render the stream. Thus, based on the topology, there may be contention for the available video or audio resources.
One such topology, shown in FIG. 1, may include two sources and five sinks, as indicated. A source number 1 wants to stream video to sink number 1 and source number 2 wants to stream video to sink number 2, the link between branch number 2 and branch number 3 is common to both paths. Thus, issues may arise at the source with respect to this contention, including how much bandwidth is available in that or any other link along the path. Another issue is how resources on the path can be reserved. Still another issue is how many audio/visual streams can be driven. Other issues include how access to shared resources can be managed and how errors can be communicated.